Increasing demand for metals caused by global economic growth and exploitation of shallow mineral deposits forces mineral extraction to go deeper. A direct consequence of this development is an increase in rock pressure-related mining problems. The role of rock engineering in the design and operation of deep mines is discussed in detail. Critical issues are the rock fracturing around mining excavations, the support and control of the fractured rock, and the rock mechanics design of mine infrastructure and extraction (stoping) systems. Progress of the science of rock mechanics in the areas related to these issues is highlighted and critically examined. Specific areas are the prediction and assessment of the mechanical properties of rock mass, the mechanics of controlling fractured rock around deep mining excavations and the resulting demands on support systems. Rock engineering aspects of stoping systems and the regional stress changes resulting from the extraction of large mineral bodies are discussed in detail. The progress in design concepts for open stopes and stopes with caving of the roof strata is illustrated. It is shown that the stress environment in deep mines does not favour the highly productive caving systems of stoping. The value of energy-based design concepts for very deep mines exploiting tabular mineral deposits is shown. Despite the considerable progress that has been made in the science of rock mechanics since the 1950s, progress in applying this knowledge to solve rock pressure problems in deep mines has been rather slow. The tools are available. What is needed is the development of robust design criteria for mine infrastructure, excavations and support systems for dynamic and changing stress environments. The second critical issue is the lack of highly qualified rock engineering personnel on the mines. This has been recognized by the European mining industry through supporting a continued education programme in rock engineering for deep mines. Keywords Rock mechanics principles • Rock engineering methods • Mine design • Design criteria • Support principles • Support methods List of Symbols Basic units m Metre kg Kilogramme (mass) s Second Derived units m² Square metre m³ Cubic metre m/s Velocity kg/m³ Density N Newton (force), 1 N = 1kg m/s 2 Pa Pascal (Pa) pressure or stress, 1Pa = 1N/m² J Joule (energy or work), 1J = 1N*1m W Watt (power), 1W = 1J/s
With the ever‐increasing depth of mines, the management of heat has become a key issue for their design and operation. There are two main sources of heat: heat transfer from the rock mass into the mine workings and heat associated with mining operations. The principles of heat transfer from the rock mass are discussed and basic relationships presented. Sources of heat linked to mining operations are discussed. It is shown that in deep‐level mines, heat transfer from the rock mass accounts more than 75 % of total mine heat load. In highly mechanized coal mines, heat from the use of mining machinery is also significant. Some models of heat flow prediction for deep gold mines are presented. It is shown that in the case of deep mines, control of heat flow is more important than increasing refrigeration capacity. Examples of heat flow management methods are given. Durch die ständig zunehmende Teufe der Abbaubetriebspunkte wird die Erdwärme zu einem Schlüsselfaktor hinsichtlich Planung und Betrieb von tiefliegenden Bergwerken. Es gibt zwei Hauptwärmequellen, einerseits den Wärmeübergang vom umgebenden Gebirge in die Grubenbaue sowie wärmeproduzierende Arbeitsvorgänge unter Tage. Dieser Beitrag erörtert die Grundsätze des Wärmetransfers aus dem Gebirge und stellt grundlegende Zusammenhänge dar. Darüber hinaus wird auf Wärmequellen im Bergbaubetrieb eingegangen. In tiefliegenden Bergwerken trägt der Wärmeübergang aus dem Gebirge mehr als 75 % zur gesamten Wärmebelastung bei, im Fall von hoch mechanisierten Kohlebergwerken ist die Wärme von Vortriebs‐ und Gewinnungsmaschinen signifikant. Einige Modelle für die Voraussagung von Wärmeströmen in tiefliegenden Goldbergwerken werden dargestellt. Es zeigt sich, dass die Kontrolle von Wärmeströmen wichtiger ist als die Erhöhung der Kühlleistung. Einige Beispiele zeigen Möglichkeiten zum Umgang mit Wärmeströmen auf.
In Part 1 of “The Management of Heat Flow in Deep Mines” the sources of heat, mechanism of heat transfer and strategies of controlling heat transfer have been discussed. Part 2 deals with the effects of heat on the human body and mine cooling strategies for deep mines. In detail the effects of heat on a worker are examined, heat stress and heat tolerance discussed and methods of assessing heat stress in different mining situations presented. Experiences from deep South African gold mines highlight the adverse effects of heat stress environment on safety and labour productivity. The principal methods of cooling of deep and ultra deep mines are discussed. It is shown that auto‐compression of ventilation air is a deciding factor governing the choice of surface or underground cooling of ventilation air. In the case of deep and ultra deep mines, the use of chilled service water and ice slurry has shown to be the most cost effective means of mine cooling. In the case of ice slurry as cooling medium advantage is taken of the latent heat of ice which significantly reduces the amount of water required for mine cooling and hence the cost of pumping the water to surface. Cooling strategies for moderately deep, deep and ultra deep mines are discussed. Examples of cooling of deep long mine tunnels are given.
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